Gas in all carburators, except one.

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  • runhan90
    • Feb 2026

    #1

    Gas in all carburators, except one.

    After cleaning up and installing a repair kit it I have run into a problem.. There is no fuel in the float bowl in carb 4.
    1, 2 and 3 fills up just fine. I removed the bowl and set the petcock on PRE. nothing happens. The vakuum-hose is also in good condition.
    Do you have any idea of what could be wrong?

    The picture was taken before i took it apart.
    Attached Files
  • tom203
    Forum Guru
    Past Site Supporter
    • Aug 2010
    • 8925
    • Norway,Maine

    #2
    Something is blocking fuel... Float stuck, unlikely..... Gunk in passage, more likely. Did you seperate the carbs from each other when you used the "repair kit"?
    1981 gs650L

    "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

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    • runhan90

      #3
      Floaters and needle seems to work fine.. Yes, i took them apart and cleaned them separately. Can it have anything to do with the vakuum hose?
      I find a lot of information on carburators in here, but its almost always the "never" vakuum types, not the mechanical wich i have.

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      • Sandy
        Forum Guru
        Past Site Supporter
        • Feb 2004
        • 7507
        • Cranbrook, BC Canada

        #4
        Fuel passage is simple and if the float valve is working fuel should flow unless something is blocked. I noticed in the photo your #2 and #4 vent tubes are linked together. These are vent tubes, not vacuum ports and should be open to atmosphere, not hooked together. Probably nothing to do with your problem if you've tested with the float bowl removed but just an observation. Has to be a blockage somewhere.
        '84 GS750EF (Oct 2015 BOM) '79 GS1000N (June 2007 BOM)

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        • runhan90

          #5
          Thanks for the reply. I?ll check for blockage tomorow then. hopefully thats it.

          Originally posted by Sandy
          Fuel passage is simple and if the float valve is working fuel should flow unless something is blocked. I noticed in the photo your #2 and #4 vent tubes are linked together. These are vent tubes, not vacuum ports and should be open to atmosphere, not hooked together. Probably nothing to do with your problem if you've tested with the float bowl removed but just an observation. Has to be a blockage somewhere.
          As I understand it, the vent tubes (not installed in the picture) is supposed to be connected on the bottom of the carb? The tube on Carb 3 is connected to the vacuum port on the petcock.

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          • allojohn
            Forum Sage
            Past Site Supporter
            Super Site Supporter
            • Jan 2011
            • 3515
            • NoMo, MN

            #6
            Originally posted by runhan90
            As I understand it, the vent tubes (not installed in the picture) is supposed to be connected on the bottom of the carb? The tube on Carb 3 is connected to the vacuum port on the petcock.
            No, the tubes on the bottom of the float bowls are for overflow. As Sandy says, the vents on carbs 2 & 4 should be open and run over the airbox.
            -Mal

            "The only reason for time is so that everything doesn't happen at once." - B. Banzai
            ___________

            78 GS750E

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            • Sandy
              Forum Guru
              Past Site Supporter
              • Feb 2004
              • 7507
              • Cranbrook, BC Canada

              #7
              Originally posted by runhan90
              Thanks for the reply. I?ll check for blockage tomorow then. hopefully thats it.



              As I understand it, the vent tubes (not installed in the picture) is supposed to be connected on the bottom of the carb? The tube on Carb 3 is connected to the vacuum port on the petcock.
              No, those are the float bowl overflow tubes. Vacuum on #3 is correct, the same port on #2 and #4 are vent tubes.

              EDIT: LOL. No fair, you can type faster.
              Last edited by Sandy; 03-07-2016, 03:16 PM.
              '84 GS750EF (Oct 2015 BOM) '79 GS1000N (June 2007 BOM)

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              • allojohn
                Forum Sage
                Past Site Supporter
                Super Site Supporter
                • Jan 2011
                • 3515
                • NoMo, MN

                #8
                Originally posted by Sandy
                EDIT: LOL. No fair, you can type faster.
                I saw you were offline, so I jumped in! You must've logged on a minute later....
                -Mal

                "The only reason for time is so that everything doesn't happen at once." - B. Banzai
                ___________

                78 GS750E

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                • hannibal
                  Forum Sage
                  • Jun 2015
                  • 1033
                  • Washington DC

                  #9
                  Maybe the fuel "line" between 3 and 4 is blocked. It's a pretty large diameter tube, so it's unlikely. Just pointing out that #4 may not be getting fuel at all.
                  Jordan

                  1977 Suzuki GS750 (My first bike)
                  2000 Kawasaki ZRX1100
                  1973 BMW R75/5

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                  • allojohn
                    Forum Sage
                    Past Site Supporter
                    Super Site Supporter
                    • Jan 2011
                    • 3515
                    • NoMo, MN

                    #10
                    Originally posted by hannibal
                    Maybe the fuel "line" between 3 and 4 is blocked. It's a pretty large diameter tube, so it's unlikely. Just pointing out that #4 may not be getting fuel at all.
                    Any chance you put the float on upside down? Yes, I have done that and it'll shut the valve very effectively......
                    -Mal

                    "The only reason for time is so that everything doesn't happen at once." - B. Banzai
                    ___________

                    78 GS750E

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                    • Guest

                      #11
                      I bet you have the carb bodies mixed up. When you look at the sides of #1 & #4, inline with where the fuel feeds are on #2 & #3, there is a hole but it is blocked on #1 & #4. If you've mixed up #3 and #4 when you look at #4 there will be a hole there where it should be blocked.........not sure if any of that made sense but it will when you look at your carbs

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                      • runhan90

                        #12
                        Originally posted by allojohn
                        Any chance you put the float on upside down? Yes, I have done that and it'll shut the valve very effectively......
                        hehe its always something easy, so this could be it. Ill check in the morning

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                        • runhan90

                          #13
                          Originally posted by azr
                          I bet you have the carb bodies mixed up. When you look at the sides of #1 & #4, inline with where the fuel feeds are on #2 & #3, there is a hole but it is blocked on #1 & #4. If you've mixed up #3 and #4 when you look at #4 there will be a hole there where it should be blocked.........not sure if any of that made sense but it will when you look at your carbs
                          I did not even think of it. Even though i marked them, the marking goes away while washing them. Thanks for the response, ill check tomorrow

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                          • runhan90

                            #14
                            All four is now working. I decided to clean the 4th carburator again, and that did the trick. Thanks for the help

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                            • tkent02
                              Forum LongTimer
                              Past Site Supporter
                              • Jan 2006
                              • 35571
                              • Near South Park

                              #15
                              It's a completely simple part of the carburetor, vacuum has nothing to do with it if fuel is getting past the petcock at all. A pipe comes across from #3, then there's the float and it's valve. That's all there is. Sometimes the float gets caught up on an aftermarket or home made gasket, but usually that makes it keep flowing to the top of the float bowl and right on out the overflow tubes at the bottom. Could also be a float just got stuck in some goo in the bowl, but again that tends to hold the float down and make it keep flowing. Take it apart and see what's blocked, let us know what you find out.
                              http://img.photobucket.com/albums/v5...tatesMap-1.jpg

                              Life is too short to ride an L.

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